<?php
/*
*  Module written/ported by Xavier Noguer <xnoguer@rezebra.com>
*
*  The majority of this is _NOT_ my code.  I simply ported it from the
*  PERL Spreadsheet::WriteExcel module.
*
*  The author of the Spreadsheet::WriteExcel module is John McNamara 
*  <jmcnamara@cpan.org>
*
*  I _DO_ maintain this code, and John McNamara has nothing to do with the
*  porting of this code to PHP.  Any questions directly related to this
*  class library should be directed to me.
*
*  License Information:
*
*	Spreadsheet::WriteExcel:  A library for generating Excel Spreadsheets
*	Copyright (C) 2002 Xavier Noguer xnoguer@rezebra.com
*
*	This library is free software; you can redistribute it and/or
*	modify it under the terms of the GNU Lesser General Public
*	License as published by the Free Software Foundation; either
*	version 2.1 of the License, or (at your option) any later version.
*
*	This library is distributed in the hope that it will be useful,
*	but WITHOUT ANY WARRANTY; without even the implied warranty of
*	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
*	Lesser General Public License for more details.
*
*	You should have received a copy of the GNU Lesser General Public
*	License along with this library; if not, write to the Free Software
*	Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
*/

require_once('Parser.php');
require_once('BIFFwriter.php');

/**
* Class for generating Excel Spreadsheets
*
* @author Xavier Noguer <xnoguer@rezebra.com>
* @package Spreadsheet_WriteExcel
*/

class Worksheet extends BIFFwriter
{

	/**
	* Constructor
	*
	* @param string  $name		 The name of the new worksheet
	* @param integer $index		The index of the new worksheet
	* @param mixed   &$activesheet The current activesheet of the workbook we belong to
	* @param mixed   &$firstsheet  The first worksheet in the workbook we belong to 
	* @param mixed   &$url_format  The default format for hyperlinks
	* @param mixed   &$parser	  The formula parser created for the Workbook
	*/
	function Worksheet($name,$index,&$activesheet,&$firstsheet,&$url_format,&$parser)
	{
		$this->BIFFwriter();	 // It needs to call its parent's constructor explicitly
		$rowmax				= 65536; // 16384 in Excel 5
		$colmax				= 256;
		$strmax				= 255;
	
		$this->name			= $name;
		$this->index		   = $index;
		$this->activesheet	 = &$activesheet;
		$this->firstsheet	  = &$firstsheet;
		$this->_url_format	 = $url_format;
		$this->_parser		 = &$parser;
	
		$this->ext_sheets	  = array();
		$this->_using_tmpfile  = 1;
		$this->_filehandle	 = "";
		$this->fileclosed	  = 0;
		$this->offset		  = 0;
		$this->xls_rowmax	  = $rowmax;
		$this->xls_colmax	  = $colmax;
		$this->xls_strmax	  = $strmax;
		$this->dim_rowmin	  = $rowmax +1;
		$this->dim_rowmax	  = 0;
		$this->dim_colmin	  = $colmax +1;
		$this->dim_colmax	  = 0;
		$this->colinfo		 = array();
		$this->_selection	  = array(0,0,0,0);
		$this->_panes		  = array();
		$this->_active_pane	= 3;
		$this->_frozen		 = 0;
		$this->selected		= 0;
	
		$this->_paper_size	  = 0x0;
		$this->_orientation	 = 0x1;
		$this->_header		  = '';
		$this->_footer		  = '';
		$this->_hcenter		 = 0;
		$this->_vcenter		 = 0;
		$this->_margin_head	 = 0.50;
		$this->_margin_foot	 = 0.50;
		$this->_margin_left	 = 0.75;
		$this->_margin_right	= 0.75;
		$this->_margin_top	  = 1.00;
		$this->_margin_bottom   = 1.00;
	
		$this->_title_rowmin	= NULL;
		$this->_title_rowmax	= NULL;
		$this->_title_colmin	= NULL;
		$this->_title_colmax	= NULL;
		$this->_print_rowmin	= NULL;
		$this->_print_rowmax	= NULL;
		$this->_print_colmin	= NULL;
		$this->_print_colmax	= NULL;
	
		$this->_print_gridlines = 1;
		$this->_print_headers   = 0;
	
		$this->_fit_page		= 0;
		$this->_fit_width	   = 0;
		$this->_fit_height	  = 0;
	
		$this->_hbreaks		 = array();
		$this->_vbreaks		 = array();
	
		$this->_protect		 = 0;
		$this->_password		= NULL;
	
		$this->col_sizes		= array();
		$this->row_sizes		= array();
	
		$this->_zoom			= 100;
		$this->_print_scale	 = 100;
	
		$this->_initialize();
	}
	
	/**
	* Open a tmp file to store the majority of the Worksheet data. If this fails,
	* for example due to write permissions, store the data in memory. This can be
	* slow for large files.
	*/
	function _initialize()
	{
		// Open tmp file for storing Worksheet data
		$fh = tmpfile();
		if ( $fh) {
			// Store filehandle
			$this->_filehandle = $fh;
		}
		else {
			// If tmpfile() fails store data in memory
			$this->_using_tmpfile = 0;
		}
	}
	
	/**
	* Add data to the beginning of the workbook (note the reverse order)
	* and to the end of the workbook.
	*
	* @access public 
	* @see Workbook::store_workbook()
	* @param array $sheetnames The array of sheetnames from the Workbook this 
	*						  worksheet belongs to
	*/
	function close($sheetnames)
	{
		$num_sheets = count($sheetnames);

		/***********************************************
		* Prepend in reverse order!!
		*/
	
		// Prepend the sheet dimensions
		$this->_store_dimensions();
	
		// Prepend the sheet password
		$this->_store_password();
	
		// Prepend the sheet protection
		$this->_store_protect();
	
		// Prepend the page setup
		$this->_store_setup();
	
		// Prepend the bottom margin
		$this->_store_margin_bottom();
	
		// Prepend the top margin
		$this->_store_margin_top();
	
		// Prepend the right margin
		$this->_store_margin_right();
	
		// Prepend the left margin
		$this->_store_margin_left();
	
		// Prepend the page vertical centering
		$this->store_vcenter();
	
		// Prepend the page horizontal centering
		$this->store_hcenter();
	
		// Prepend the page footer
		$this->store_footer();
	
		// Prepend the page header
		$this->store_header();
	
		// Prepend the vertical page breaks
		$this->_store_vbreak();
	
		// Prepend the horizontal page breaks
		$this->_store_hbreak();
	
		// Prepend WSBOOL
		$this->_store_wsbool();
	
		// Prepend GRIDSET
		$this->_store_gridset();
	
		// Prepend PRINTGRIDLINES
		$this->_store_print_gridlines();
	
		// Prepend PRINTHEADERS
		$this->_store_print_headers();
	
		// Prepend EXTERNSHEET references
		for ($i = $num_sheets; $i > 0; $i--) {
			$sheetname = $sheetnames[$i-1];
			$this->_store_externsheet($sheetname);
		}
	
		// Prepend the EXTERNCOUNT of external references.
		$this->_store_externcount($num_sheets);
	
		// Prepend the COLINFO records if they exist
		if (!empty($this->colinfo)){
			for($i=0; $i < count($this->colinfo); $i++)
			{
				$this->_store_colinfo($this->colinfo[$i]);
			}
			$this->_store_defcol();
		}
	
		// Prepend the BOF record
		$this->_store_bof(0x0010);
	
		/*
		* End of prepend. Read upwards from here.
		***********************************************/
	
		// Append
		$this->_store_window2();
		$this->_store_zoom();
		if(!empty($this->_panes))
		  $this->_store_panes($this->_panes);
		$this->_store_selection($this->_selection);
		$this->_store_eof();
	}
	
	/**
	* Retrieve the worksheet name. This is usefull when creating worksheets
	* without a name.
	*
	* @access public
	* @return string The worksheet's name
	*/
	function get_name()
	{
		return($this->name);
	}
	
	/**
	* Retrieves data from memory in one chunk, or from disk in $buffer
	* sized chunks.
	*
	* @return string The data
	*/
	function get_data()
	{
		$buffer = 4096;
	
		// Return data stored in memory
		if (isset($this->_data)) {
			$tmp   = $this->_data;
			unset($this->_data);
			$fh	= $this->_filehandle;
			if ($this->_using_tmpfile) {
				fseek($fh, 0);
			}
			return($tmp);
		}
		// Return data stored on disk
		if ($this->_using_tmpfile) {
			if ($tmp = fread($this->_filehandle, $buffer)) {
				return($tmp);
			}
		}
	
		// No data to return
		return('');
	}
	
	/**
	* Set this worksheet as a selected worksheet, i.e. the worksheet has its tab
	* highlighted.
	*
	* @access public
	*/
	function select()
	{
		$this->selected = 1;
	}
	
	/**
	* Set this worksheet as the active worksheet, i.e. the worksheet that is
	* displayed when the workbook is opened. Also set it as selected.
	*
	* @access public
	*/
	function activate()
	{
		$this->selected = 1;
		$this->activesheet =& $this->index;
	}
	
	/**
	* Set this worksheet as the first visible sheet. This is necessary
	* when there are a large number of worksheets and the activated
	* worksheet is not visible on the screen.
	*
	* @access public
	*/
	function set_first_sheet()
	{
		$this->firstsheet = $this->index;
	}
	
	/**
	* Set the worksheet protection flag to prevent accidental modification and to
	* hide formulas if the locked and hidden format properties have been set.
	*
	* @access public
	* @param string $password The password to use for protecting the sheet.
	*/
	function protect($password)
	{
		$this->_protect   = 1;
		$this->_password  = $this->_encode_password($password);
	}
	
	/**
	* Set the width of a single column or a range of columns.
	*
	* @access public
	* @see _store_colinfo()
	* @param integer $firstcol first column on the range
	* @param integer $lastcol  last column on the range
	* @param integer $width	width to set
	* @param mixed   $format   The optional XF format to apply to the columns
	* @param integer $hidden   The optional hidden atribute
	*/
	function set_column($firstcol, $lastcol, $width, $format = 0, $hidden = 0)
	{
		$this->colinfo[] = array($firstcol, $lastcol, $width, $format, $hidden);

		// Set width to zero if column is hidden
		$width = ($hidden) ? 0 : $width;
	
		for($col = $firstcol; $col <= $lastcol; $col++) {
			$this->col_sizes[$col] = $width;
		}
	}
	
	/**
	* Set which cell or cells are selected in a worksheet
	*
	* @access public
	* @param integer $first_row	first row in the selected quadrant
	* @param integer $first_column first column in the selected quadrant
	* @param integer $last_row	 last row in the selected quadrant
	* @param integer $last_column  last column in the selected quadrant
	* @see _store_selection()
	*/
	function set_selection($first_row,$first_column,$last_row,$last_column)
	{
		$this->_selection = array($first_row,$first_column,$last_row,$last_column);
	}
	
	/**
	* Set panes and mark them as frozen.
	*
	* @access public
	* @param array $panes This is the only parameter received and is composed of the following:
	*					 0 => Vertical split position,
	*					 1 => Horizontal split position
	*					 2 => Top row visible
	*					 3 => Leftmost column visible
	*					 4 => Active pane
	*/
	function freeze_panes($panes)
	{
		$this->_frozen = 1;
		$this->_panes  = $panes;
	}
	
	/**
	* Set panes and mark them as unfrozen.
	*
	* @access public
	* @param array $panes This is the only parameter received and is composed of the following:
	*					 0 => Vertical split position,
	*					 1 => Horizontal split position
	*					 2 => Top row visible
	*					 3 => Leftmost column visible
	*					 4 => Active pane
	*/
	function thaw_panes($panes)
	{
		$this->_frozen = 0;
		$this->_panes  = $panes;
	}
	
	/**
	* Set the page orientation as portrait.
	*
	* @access public
	*/
	function set_portrait()
	{
		$this->_orientation = 1;
	}
	
	/**
	* Set the page orientation as landscape.
	*
	* @access public
	*/
	function set_landscape()
	{
		$this->_orientation = 0;
	}
	
	/**
	* Set the paper type. Ex. 1 = US Letter, 9 = A4
	*
	* @access public
	* @param integer $size The type of paper size to use
	*/
	function set_paper($size = 0)
	{
		$this->_paper_size = $size;
	}
	
	
	/**
	* Set the page header caption and optional margin.
	*
	* @access public
	* @param string $string The header text
	* @param float  $margin optional head margin in inches.
	*/
	function set_header($string,$margin = 0.50)
	{
		if (strlen($string) >= 255) {
			//carp 'Header string must be less than 255 characters';
			return;
		}
		$this->_header	  = $string;
		$this->_margin_head = $margin;
	}
	
	/**
	* Set the page footer caption and optional margin.
	*
	* @access public
	* @param string $string The footer text
	* @param float  $margin optional foot margin in inches.
	*/
	function set_footer($string,$margin = 0.50)
	{
		if (strlen($string) >= 255) {
			//carp 'Footer string must be less than 255 characters';
			return;
		}
		$this->_footer	  = $string;
		$this->_margin_foot = $margin;
	}
	
	/**
	* Center the page horinzontally.
	*
	* @access public
	* @param integer $center the optional value for centering. Defaults to 1 (center).
	*/
	function center_horizontally($center = 1)
	{
		$this->_hcenter = $center;
	}
	
	/**
	* Center the page horinzontally.
	*
	* @access public
	* @param integer $center the optional value for centering. Defaults to 1 (center).
	*/
	function center_vertically($center = 1)
	{
		$this->_vcenter = $center;
	}
	
	/**
	* Set all the page margins to the same value in inches.
	*
	* @access public
	* @param float $margin The margin to set in inches
	*/
	function set_margins($margin)
	{
		$this->set_margin_left($margin);
		$this->set_margin_right($margin);
		$this->set_margin_top($margin);
		$this->set_margin_bottom($margin);
	}
	
	/**
	* Set the left and right margins to the same value in inches.
	*
	* @access public
	* @param float $margin The margin to set in inches
	*/
	function set_margins_LR($margin)
	{
		$this->set_margin_left($margin);
		$this->set_margin_right($margin);
	}
	
	/**
	* Set the top and bottom margins to the same value in inches.
	*
	* @access public
	* @param float $margin The margin to set in inches
	*/
	function set_margins_TB($margin)
	{
		$this->set_margin_top($margin);
		$this->set_margin_bottom($margin);
	}
	
	/**
	* Set the left margin in inches.
	*
	* @access public
	* @param float $margin The margin to set in inches
	*/
	function set_margin_left($margin = 0.75)
	{
		$this->_margin_left = $margin;
	}
	
	/**
	* Set the right margin in inches.
	*
	* @access public
	* @param float $margin The margin to set in inches
	*/
	function set_margin_right($margin = 0.75)
	{
		$this->_margin_right = $margin;
	}
	
	/**
	* Set the top margin in inches.
	*
	* @access public
	* @param float $margin The margin to set in inches
	*/
	function set_margin_top($margin = 1.00)
	{
		$this->_margin_top = $margin;
	}
	
	/**
	* Set the bottom margin in inches.
	*
	* @access public
	* @param float $margin The margin to set in inches
	*/
	function set_margin_bottom($margin = 1.00)
	{
		$this->_margin_bottom = $margin;
	}
	
	/**
	* Set the rows to repeat at the top of each printed page. See also the
	* _store_name_xxxx() methods in Workbook.php
	*
	* @access public
	* @param integer $first_row First row to repeat
	* @param integer $last_row  Last row to repeat. Optional.
	*/
	function repeat_rows($first_row, $last_row = NULL)
	{
		$this->_title_rowmin  = $first_row;
		if(isset($last_row)) { //Second row is optional
			$this->_title_rowmax  = $last_row;
		}
		else {
			$this->_title_rowmax  = $first_row;
		}
	}
	
	/**
	* Set the columns to repeat at the left hand side of each printed page.
	* See also the _store_names() methods in Workbook.php
	*
	* @access public
	* @param integer $first_col First column to repeat
	* @param integer $last_col  Last column to repeat. Optional.
	*/
	function repeat_columns($first_col, $last_col = NULL)
	{
		$this->_title_colmin  = $first_col;
		if(isset($last_col)) { // Second col is optional
			$this->_title_colmax  = $last_col;
		}
		else {
			$this->_title_colmax  = $first_col;
		}
	}
	
	/**
	* Set the area of each worksheet that will be printed.
	*
	* @access public
	* @see Workbook::_store_names()
	* @param integer $first_row First row of the area to print
	* @param integer $first_col First column of the area to print
	* @param integer $last_row  Last row of the area to print
	* @param integer $last_col  Last column of the area to print
	*/
	function print_area($first_row, $first_col, $last_row, $last_col)
	{
		$this->_print_rowmin  = $first_row;
		$this->_print_colmin  = $first_col;
		$this->_print_rowmax  = $last_row;
		$this->_print_colmax  = $last_col;
	}
	
	
	/**
	* Set the option to hide gridlines on the printed page. 
	*
	* @access public
	* @see _store_print_gridlines(), _store_gridset()
	*/
	function hide_gridlines()
	{
		$this->_print_gridlines = 0;
	}
	
	/**
	* Set the option to print the row and column headers on the printed page.
	* See also the _store_print_headers() method below.
	*
	* @access public
	* @see _store_print_headers()
	* @param integer $print Whether to print the headers or not. Defaults to 1 (print).
	*/
	function print_row_col_headers($print = 1)
	{
		$this->_print_headers = $print;
	}
	
	/**
	* Store the vertical and horizontal number of pages that will define the
	* maximum area printed. It doesn't seem to work with OpenOffice.
	*
	* @access public
	* @param  integer $width  Maximun width of printed area in pages
	* @param  integer $heigth Maximun heigth of printed area in pages
	* @see set_print_scale()
	*/
	function fit_to_pages($width, $height)
	{
		$this->_fit_page	  = 1;
		$this->_fit_width	 = $width;
		$this->_fit_height	= $height;
	}
	
	/**
	* Store the horizontal page breaks on a worksheet (for printing).
	* The breaks represent the row after which the break is inserted.
	*
	* @access public
	* @param array $breaks Array containing the horizontal page breaks
	*/
	function set_h_pagebreaks($breaks)
	{
		foreach($breaks as $break) {
			array_push($this->_hbreaks,$break);
		}
	}
	
	/**
	* Store the vertical page breaks on a worksheet (for printing).
	* The breaks represent the column after which the break is inserted.
	*
	* @access public
	* @param array $breaks Array containing the vertical page breaks
	*/
	function set_v_pagebreaks($breaks)
	{
		foreach($breaks as $break) {
			array_push($this->_vbreaks,$break);
		}
	}
	
	
	/**
	* Set the worksheet zoom factor.
	*
	* @access public
	* @param integer $scale The zoom factor
	*/
	function set_zoom($scale = 100)
	{
		// Confine the scale to Excel's range
		if ($scale < 10 or $scale > 400) {
			//carp "Zoom factor $scale outside range: 10 <= zoom <= 400";
			$scale = 100;
		}
	
		$this->_zoom = floor($scale);
	}
	
	/**
	* Set the scale factor for the printed page. 
	* It turns off the "fit to page" option
	*
	* @access public
	* @param integer $scale The optional scale factor. Defaults to 100
	*/
	function set_print_scale($scale = 100)
	{
		// Confine the scale to Excel's range
		if ($scale < 10 or $scale > 400)
		{
			// REPLACE THIS FOR A WARNING
			die("Print scale $scale outside range: 10 <= zoom <= 400");
			$scale = 100;
		}
	
		// Turn off "fit to page" option
		$this->_fit_page	= 0;
	
		$this->_print_scale = floor($scale);
	}
	
	/**
	* Map to the appropriate write method acording to the token recieved.
	*
	* @access public
	* @param integer $row	The row of the cell we are writing to
	* @param integer $col	The column of the cell we are writing to
	* @param mixed   $token  What we are writing
	* @param mixed   $format The optional format to apply to the cell
	*/
	function write($row, $col, $token, $format = 0)
	{
		// Check for a cell reference in A1 notation and substitute row and column
		/*if ($_[0] =~ /^\D/) {
			@_ = $this->_substitute_cellref(@_);
	}*/
	
		/*
		# Match an array ref.
		if (ref $token eq "ARRAY") {
			return $this->write_row(@_);
	}*/
	
		// Match number
		if (preg_match("/^([+-]?)(?=\d|\.\d)\d*(\.\d*)?([Ee]([+-]?\d+))?$/",$token)) {
			return $this->write_number($row,$col,$token,$format);
		}
		// Match http or ftp URL
		elseif (preg_match("/^[fh]tt?p:\/\//",$token)) {
			return $this->write_url($row, $col, $token, $format);
		}
		// Match mailto:
		elseif (preg_match("/^mailto:/",$token)) {
			return $this->write_url($row, $col, $token, $format);
		}
		// Match internal or external sheet link
		elseif (preg_match("/^(?:in|ex)ternal:/",$token)) {
			return $this->write_url($row, $col, $token, $format);
		}
		// Match formula
		elseif (preg_match("/^=/",$token)) {
			return $this->write_formula($row, $col, $token, $format);
		}
		// Match formula
		elseif (preg_match("/^@/",$token)) {
			return $this->write_formula($row, $col, $token, $format);
		}
		// Match blank
		elseif ($token == '') {
			return $this->write_blank($row,$col,$format);
		}
		// Default: match string
		else {
			return $this->write_string($row,$col,$token,$format);
		}
	}
 
	/**
	* Returns an index to the XF record in the workbook
	*
	* @param mixed $format The optional XF format
	* @return integer The XF record index
	*/
	function _XF(&$format)
	{
		if($format != 0)
		{
			return($format->get_xf_index());
		}
		else
		{
			return(0x0F);
		}
	}
	
	
	/******************************************************************************
	*******************************************************************************
	*
	* Internal methods
	*/
	
	
	/**
	* Store Worksheet data in memory using the parent's class append() or to a
	* temporary file, the default.
	*
	* @param string $data The binary data to append
	*/
	function _append($data)
	{
		if ($this->_using_tmpfile)
		{
			// Add CONTINUE records if necessary
			if (strlen($data) > $this->_limit) {
				$data = $this->_add_continue($data);
			}
			fwrite($this->_filehandle,$data);
			$this->_datasize += strlen($data);
		}
		else {
			parent::_append($data);
		}
	}
	
	/**
	* Substitute an Excel cell reference in A1 notation for  zero based row and
	* column values in an argument list.
	*
	* Ex: ("A4", "Hello") is converted to (3, 0, "Hello").
	*
	* @param string $cell The cell reference. Or range of cells.
	* @return array
	*/
	function _substitute_cellref($cell)
	{
		$cell = strtoupper($cell);
	
		// Convert a column range: 'A:A' or 'B:G'
		if (preg_match("/([A-I]?[A-Z]):([A-I]?[A-Z])/",$cell,$match)) {
			list($no_use, $col1) =  $this->_cell_to_rowcol($match[1] .'1'); // Add a dummy row
			list($no_use, $col2) =  $this->_cell_to_rowcol($match[2] .'1'); // Add a dummy row
			return(array($col1, $col2));
		}
	
		// Convert a cell range: 'A1:B7'
		if (preg_match("/\$?([A-I]?[A-Z]\$?\d+):\$?([A-I]?[A-Z]\$?\d+)/",$cell,$match)) {
			list($row1, $col1) =  $this->_cell_to_rowcol($match[1]);
			list($row2, $col2) =  $this->_cell_to_rowcol($match[2]);
			return(array($row1, $col1, $row2, $col2));
		}
	
		// Convert a cell reference: 'A1' or 'AD2000'
		if (preg_match("/\$?([A-I]?[A-Z]\$?\d+)/",$cell)) {
			list($row1, $col1) =  $this->_cell_to_rowcol($match[1]);
			return(array($row1, $col1));
		}
	
		die("Unknown cell reference $cell ");
	}
	
	/**
	* Convert an Excel cell reference in A1 notation to a zero based row and column
	* reference; converts C1 to (0, 2).
	*
	* @param string $cell The cell reference.
	* @return array containing (row, column)
	*/
	function _cell_to_rowcol($cell)
	{
		preg_match("/\$?([A-I]?[A-Z])\$?(\d+)/",$cell,$match);
		$col	 = $match[1];
		$row	 = $match[2];
	
		// Convert base26 column string to number
		$chars = split('', $col);
		$expn  = 0;
		$col   = 0;
	
		while ($chars) {
			$char = array_pop($chars);		// LS char first
			$col += (ord($char) -ord('A') +1) * pow(26,$expn);
			$expn++;
		}
	
		// Convert 1-index to zero-index
		$row--;
		$col--;
	
		return(array($row, $col));
	}
	
	/**
	* Based on the algorithm provided by Daniel Rentz of OpenOffice.
	*
	* @param string $plaintext The password to be encoded in plaintext.
	* @return string The encoded password
	*/
	function _encode_password($plaintext)
	{
		$password = 0x0000;
		$i		= 1;	   // char position
 
		// split the plain text password in its component characters
		$chars = preg_split('//', $plaintext, -1, PREG_SPLIT_NO_EMPTY);
		foreach($chars as $char)
		{
			$value	 = ord($char) << $i;   // shifted ASCII value 
			$bit_16	= $value & 0x8000;	// the bit 16
			$bit_16  >>= 15;				 // 0x0000 or 0x0001
			//$bit_17	= $value & 0x00010000;
			//$bit_17  >>= 15;
			$value	&= 0x7fff;			 // first 15 bits
			$password ^= ($value | $bit_16);
			//$password ^= ($value | $bit_16 | $bit_17);
			$i++;
		}
	
		$password ^= strlen($plaintext);
		$password ^= 0xCE4B;

		return($password);
	}
	
	/******************************************************************************
	*******************************************************************************
	*
	* BIFF RECORDS
	*/
	
	
	/**
	* Write a double to the specified row and column (zero indexed).
	* An integer can be written as a double. Excel will display an
	* integer. $format is optional.
	*
	* Returns  0 : normal termination
	*		 -2 : row or column out of range
	*
	* @access public
	* @param integer $row	Zero indexed row
	* @param integer $col	Zero indexed column
	* @param float   $num	The number to write
	* @param mixed   $format The optional XF format
	*/
	function write_number($row, $col, $num, $format = 0)
	{
		$record	= 0x0203;				 // Record identifier
		$length	= 0x000E;				 // Number of bytes to follow
		$xf		= $this->_XF($format);	// The cell format
	
		// Check that row and col are valid and store max and min values
		if ($row >= $this->xls_rowmax)
		{
			return(-2);
		}
		if ($col >= $this->xls_colmax)
		{
			return(-2);
		}
		if ($row <  $this->dim_rowmin) 
		{
			$this->dim_rowmin = $row;
		}
		if ($row >  $this->dim_rowmax) 
		{
			$this->dim_rowmax = $row;
		}
		if ($col <  $this->dim_colmin) 
		{
			$this->dim_colmin = $col;
		}
		if ($col >  $this->dim_colmax) 
		{
			$this->dim_colmax = $col;
		}
	
		$header	= pack("vv",  $record, $length);
		$data	  = pack("vvv", $row, $col, $xf);
		$xl_double = pack("d",   $num);
		if ($this->_byte_order) // if it's Big Endian
		{
			$xl_double = strrev($xl_double);
		}
	
		$this->_append($header.$data.$xl_double);
		return(0);
	}
	
	/**
	* Write a string to the specified row and column (zero indexed).
	* NOTE: there is an Excel 5 defined limit of 255 characters.
	* $format is optional.
	* Returns  0 : normal termination
	*		 -1 : insufficient number of arguments
	*		 -2 : row or column out of range
	*		 -3 : long string truncated to 255 chars
	*
	* @access public
	* @param integer $row	Zero indexed row
	* @param integer $col	Zero indexed column
	* @param string  $str	The string to write
	* @param mixed   $format The XF format for the cell
	*/
	function write_string($row, $col, $str, $format = 0)
	{
		$strlen	= strlen($str);
		$record	= 0x0204;				   // Record identifier
		$length	= 0x0008 + $strlen;		 // Bytes to follow
		$xf		= $this->_XF($format);	  // The cell format
		
		$str_error = 0;
	
		// Check that row and col are valid and store max and min values
		if ($row >= $this->xls_rowmax) 
		{
			return(-2);
		}
		if ($col >= $this->xls_colmax) 
		{
			return(-2);
		}
		if ($row <  $this->dim_rowmin) 
		{
			$this->dim_rowmin = $row;
		}
		if ($row >  $this->dim_rowmax) 
		{
			$this->dim_rowmax = $row;
		}
		if ($col <  $this->dim_colmin) 
		{
			$this->dim_colmin = $col;
		}
		if ($col >  $this->dim_colmax) 
		{
			$this->dim_colmax = $col;
		}
	
		if ($strlen > $this->xls_strmax)  // LABEL must be < 255 chars
		{
			$str	   = substr($str, 0, $this->xls_strmax);
			$length	= 0x0008 + $this->xls_strmax;
			$strlen	= $this->xls_strmax;
			$str_error = -3;
		}
	
		$header	= pack("vv",   $record, $length);
		$data	  = pack("vvvv", $row, $col, $xf, $strlen);
		$this->_append($header.$data.$str);
		return($str_error);
	}
 
	/**
	* Writes a note associated with the cell given by the row and column.
	* NOTE records don't have a length limit.
	*
	* @access public
	* @param integer $row	Zero indexed row
	* @param integer $col	Zero indexed column
	* @param string  $note   The note to write
	*/
	function write_note($row, $col, $note)
	{
		$note_length	= strlen($note);
		$record		 = 0x001C;				// Record identifier
		$max_length	 = 2048;				  // Maximun length for a NOTE record
		//$length	  = 0x0006 + $note_length;	// Bytes to follow

		// Check that row and col are valid and store max and min values
		if ($row >= $this->xls_rowmax) 
		{
			return(-2);
		}
		if ($col >= $this->xls_colmax) 
		{
			return(-2);
		}
		if ($row <  $this->dim_rowmin) 
		{
			$this->dim_rowmin = $row;
		}
		if ($row >  $this->dim_rowmax) 
		{
			$this->dim_rowmax = $row;
		}
		if ($col <  $this->dim_colmin) 
		{
			$this->dim_colmin = $col;
		}
		if ($col >  $this->dim_colmax) 
		{
			$this->dim_colmax = $col;
		}
 
		// Length for this record is no more than 2048 + 6
		$length	= 0x0006 + min($note_length, 2048);
		$header	= pack("vv",   $record, $length);
		$data	  = pack("vvv", $row, $col, $note_length);
		$this->_append($header.$data.substr($note, 0, 2048));

		for($i = $max_length; $i < $note_length; $i += $max_length)
		{
			$chunk  = substr($note, $i, $max_length);
			$length = 0x0006 + strlen($chunk);
			$header = pack("vv",   $record, $length);
			$data   = pack("vvv", -1, 0, strlen($chunk));
			$this->_append($header.$data.$chunk);
		}
		return(0);
	}
 
	/**
	* Write a blank cell to the specified row and column (zero indexed).
	* A blank cell is used to specify formatting without adding a string
	* or a number.
	*
	* A blank cell without a format serves no purpose. Therefore, we don't write
	* a BLANK record unless a format is specified. This is mainly an optimisation
	* for the write_row() and write_col() methods.
	*
	* Returns  0 : normal termination (including no format)
	*		 -1 : insufficient number of arguments
	*		 -2 : row or column out of range
	*
	* @access public
	* @param integer $row	Zero indexed row
	* @param integer $col	Zero indexed column
	* @param mixed   $format The XF format
	*/
	function write_blank($row, $col, $format = 0)
	{
		// Don't write a blank cell unless it has a format
		if ($format == 0)
		{
			return(0);
		}
	
		$record	= 0x0201;				 // Record identifier
		$length	= 0x0006;				 // Number of bytes to follow
		$xf		= $this->_XF($format);	// The cell format
	
		// Check that row and col are valid and store max and min values
		if ($row >= $this->xls_rowmax) 
		{
			return(-2);
		}
		if ($col >= $this->xls_colmax) 
		{
			return(-2);
		}
		if ($row <  $this->dim_rowmin) 
		{
			$this->dim_rowmin = $row;
		}
		if ($row >  $this->dim_rowmax) 
		{
			$this->dim_rowmax = $row;
		}
		if ($col <  $this->dim_colmin) 
		{
			$this->dim_colmin = $col;
		}
		if ($col >  $this->dim_colmax) 
		{
			$this->dim_colmax = $col;
		}
	
		$header	= pack("vv",  $record, $length);
		$data	  = pack("vvv", $row, $col, $xf);
		$this->_append($header.$data);
		return 0;
	}
 
	/**
	* Write a formula to the specified row and column (zero indexed).
	* The textual representation of the formula is passed to the parser in
	* Parser.php which returns a packed binary string.
	*
	* Returns  0 : normal termination
	*		 -2 : row or column out of range
	*
	* @access public
	* @param integer $row	 Zero indexed row
	* @param integer $col	 Zero indexed column
	* @param string  $formula The formula text string
	* @param mixed   $format  The optional XF format
	*/
	function write_formula($row, $col, $formula, $format = 0)
	{
		$record	= 0x0006;	 // Record identifier
	
		// Excel normally stores the last calculated value of the formula in $num.
		// Clearly we are not in a position to calculate this a priori. Instead
		// we set $num to zero and set the option flags in $grbit to ensure
		// automatic calculation of the formula when the file is opened.
		//
		$xf		= $this->_XF($format); // The cell format
		$num	   = 0x00;				// Current value of formula
		$grbit	 = 0x03;				// Option flags
		$chn	   = 0x0000;			  // Must be zero
	
	
		// Check that row and col are valid and store max and min values
		if ($row >= $this->xls_rowmax)
		{
			return(-2);
		}
		if ($col >= $this->xls_colmax)
		{
			return(-2);
		}
		if ($row <  $this->dim_rowmin) 
		{
			$this->dim_rowmin = $row;
		}
		if ($row >  $this->dim_rowmax) 
		{
			$this->dim_rowmax = $row;
		}
		if ($col <  $this->dim_colmin) 
		{
			$this->dim_colmin = $col;
		}
		if ($col >  $this->dim_colmax) 
		{
			$this->dim_colmax = $col;
		}
	
		// Strip the '=' or '@' sign at the beginning of the formula string
		if (ereg("^=",$formula)) {
			$formula = preg_replace("/(^=)/","",$formula);
		}
		elseif(ereg("^@",$formula)) {
			$formula = preg_replace("/(^@)/","",$formula);
		}
		else {
			die("Unrecognised character for formula");
		}
	
		// Parse the formula using the parser in Parser.php
		//$tree	  = new Parser($this->_byte_order);
		$this->_parser->parse($formula);
		//$tree->parse($formula);
		$formula = $this->_parser->to_reverse_polish();
	
		$formlen	= strlen($formula);	// Length of the binary string
		$length	 = 0x16 + $formlen;	 // Length of the record data
	
		$header	= pack("vv",	  $record, $length);
		$data	  = pack("vvvdvVv", $row, $col, $xf, $num,
									 $grbit, $chn, $formlen);
	
		$this->_append($header.$data.$formula);
		return 0;
	}
	
	/**
	* Write a hyperlink. This is comprised of two elements: the visible label and
	* the invisible link. The visible label is the same as the link unless an
	* alternative string is specified. The label is written using the
	* write_string() method. Therefore the 255 characters string limit applies.
	* $string and $format are optional and their order is interchangeable.
	*
	* The hyperlink can be to a http, ftp, mail, internal sheet, or external
	* directory url.
	*
	* Returns  0 : normal termination
	*		 -1 : insufficient number of arguments
	*		 -2 : row or column out of range
	*		 -3 : long string truncated to 255 chars
	*
	* @access public
	* @param integer $row	Row
	* @param integer $col	Column
	* @param string  $url	URL string
	* @param string  $string Alternative label
	* @param mixed   $format The cell format
	*/
	function write_url($row, $col, $url, $string = '', $format = 0)
	{
		// Add start row and col to arg list
		return($this->_write_url_range($row, $col, $row, $col, $url, $string, $format));
	}
	
	/**
	* This is the more general form of write_url(). It allows a hyperlink to be
	* written to a range of cells. This function also decides the type of hyperlink
	* to be written. These are either, Web (http, ftp, mailto), Internal
	* (Sheet1!A1) or external ('c:\temp\foo.xls#Sheet1!A1').
	*
	* See also write_url() above for a general description and return values.
	*
	* @param integer $row1   Start row
	* @param integer $col1   Start column
	* @param integer $row2   End row
	* @param integer $col2   End column
	* @param string  $url	URL string
	* @param string  $string Alternative label
	* @param mixed   $format The cell format
	*/
	
	function _write_url_range($row1, $col1, $row2, $col2, $url, $string = '', $format = 0)
	{
		// Check for internal/external sheet links or default to web link
		if (preg_match('[^internal:]', $url)) {
			return($this->_write_url_internal($row1, $col1, $row2, $col2, $url, $string, $format));
		}
		if (preg_match('[^external:]', $url)) {
			return($this->_write_url_external($row1, $col1, $row2, $col2, $url, $string, $format));
		}
		return($this->_write_url_web($row1, $col1, $row2, $col2, $url, $string, $format));
	}
	
	
	/**
	* Used to write http, ftp and mailto hyperlinks.
	* The link type ($options) is 0x03 is the same as absolute dir ref without
	* sheet. However it is differentiated by the $unknown2 data stream.
	*
	* @see write_url()
	* @param integer $row1   Start row
	* @param integer $col1   Start column
	* @param integer $row2   End row
	* @param integer $col2   End column
	* @param string  $url	URL string
	* @param string  $str	Alternative label
	* @param mixed   $format The cell format
	*/
	function _write_url_web($row1, $col1, $row2, $col2, $url, $str, $format = 0)
	{
		$record	  = 0x01B8;					   // Record identifier
		$length	  = 0x00000;					  // Bytes to follow
	
		if($format == 0) {
			$format = $this->_url_format;
		}
	
		// Write the visible label using the write_string() method.
		if($str == '') {
			$str = $url;
		}
		$str_error = $this->write_string($row1, $col1, $str, $format);
		if ($str_error == -2) {
			return($str_error);
		}
	
		// Pack the undocumented parts of the hyperlink stream
		$unknown1	= pack("H*", "D0C9EA79F9BACE118C8200AA004BA90B02000000");
		$unknown2	= pack("H*", "E0C9EA79F9BACE118C8200AA004BA90B");
	
		// Pack the option flags
		$options	 = pack("V", 0x03);
	
		// Convert URL to a null terminated wchar string
		$url		 = join("\0", preg_split("''", $url, -1, PREG_SPLIT_NO_EMPTY));
		$url		 = $url . "\0\0\0";
	
		// Pack the length of the URL
		$url_len	 = pack("V", strlen($url));
	
		// Calculate the data length
		$length	  = 0x34 + strlen($url);
	
		// Pack the header data
		$header	  = pack("vv",   $record, $length);
		$data		= pack("vvvv", $row1, $row2, $col1, $col2);
	
		// Write the packed data
		$this->_append( $header. $data.
						$unknown1. $options.
						$unknown2. $url_len. $url);
		return($str_error);
	}
	
	/**
	* Used to write internal reference hyperlinks such as "Sheet1!A1".
	*
	* @see write_url()
	* @param integer $row1   Start row
	* @param integer $col1   Start column
	* @param integer $row2   End row
	* @param integer $col2   End column
	* @param string  $url	URL string
	* @param string  $str	Alternative label
	* @param mixed   $format The cell format
	*/
	function _write_url_internal($row1, $col1, $row2, $col2, $url, $str, $format = 0)
	{
		$record	  = 0x01B8;					   // Record identifier
		$length	  = 0x00000;					  // Bytes to follow
	
		if ($format == 0) {
			$format = $this->_url_format;
		}
	
		// Strip URL type
		$url = preg_replace('s[^internal:]', '', $url);
	
		// Write the visible label
		if($str == '') {
			$str = $url;
		}
		$str_error = $this->write_string($row1, $col1, $str, $format);
		if ($str_error == -2) {
			return($str_error);
		}
	
		// Pack the undocumented parts of the hyperlink stream
		$unknown1	= pack("H*", "D0C9EA79F9BACE118C8200AA004BA90B02000000");
	
		// Pack the option flags
		$options	 = pack("V", 0x08);
	
		// Convert the URL type and to a null terminated wchar string
		$url		 = join("\0", preg_split("''", $url, -1, PREG_SPLIT_NO_EMPTY));
		$url		 = $url . "\0\0\0";
	
		// Pack the length of the URL as chars (not wchars)
		$url_len	 = pack("V", floor(strlen($url)/2));
	
		// Calculate the data length
		$length	  = 0x24 + strlen($url);
	
		// Pack the header data
		$header	  = pack("vv",   $record, $length);
		$data		= pack("vvvv", $row1, $row2, $col1, $col2);
	
		// Write the packed data
		$this->_append($header. $data.
					   $unknown1. $options.
					   $url_len. $url);
		return($str_error);
	}
	
	/**
	* Write links to external directory names such as 'c:\foo.xls',
	* c:\foo.xls#Sheet1!A1', '../../foo.xls'. and '../../foo.xls#Sheet1!A1'.
	*
	* Note: Excel writes some relative links with the $dir_long string. We ignore
	* these cases for the sake of simpler code.
	*
	* @see write_url()
	* @param integer $row1   Start row
	* @param integer $col1   Start column
	* @param integer $row2   End row
	* @param integer $col2   End column
	* @param string  $url	URL string
	* @param string  $str	Alternative label
	* @param mixed   $format The cell format
	*/
	function _write_url_external($row1, $col1, $row2, $col2, $url, $str, $format = 0)
	{
		// Network drives are different. We will handle them separately
		// MS/Novell network drives and shares start with \\
		if (preg_match('[^external:\\\\]', $url)) {
			return($this->_write_url_external_net($row1, $col1, $row2, $col2, $url, $str, $format));
		}
	
		$record	  = 0x01B8;					   // Record identifier
		$length	  = 0x00000;					  // Bytes to follow
	
		if ($format == 0) {
			$format = $this->_url_format;
		}
	
		// Strip URL type and change Unix dir separator to Dos style (if needed)
		//
		$url = preg_replace('[^external:]', '', $url);
		$url = preg_replace('[/]', "\\", $url);
	
		// Write the visible label
		if ($str == '') {
			$str = preg_replace('[\#]', ' - ', $url);
		}
		$str_error = $this->write_string($row1, $col1, $str, $format);
		if ($str_error == -2) {
			return($str_error);
		}
	
		// Determine if the link is relative or absolute:
		//   relative if link contains no dir separator, "somefile.xls"
		//   relative if link starts with up-dir, "..\..\somefile.xls"
		//   otherwise, absolute
		
		$absolute	= 0x02; // Bit mask
		if (!preg_match('[\\]', $url)) {
			$absolute	= 0x00;
		}
		if (preg_match('[^\.\.\\]', $url)) {
			$absolute	= 0x00;
		}
	
		// Determine if the link contains a sheet reference and change some of the
		// parameters accordingly.
		// Split the dir name and sheet name (if it exists)
		list($dir_long , $sheet) = split('/\#/', $url);
		$link_type			   = 0x01 | $absolute;
	
		if (isset($sheet)) {
			$link_type |= 0x08;
			$sheet_len  = pack("V", strlen($sheet) + 0x01);
			$sheet	  = join("\0", split('', $sheet));
			$sheet	 .= "\0\0\0";
		}
		else {
			$sheet_len   = '';
			$sheet	   = '';
		}
	
		// Pack the link type
		$link_type   = pack("V", $link_type);
	
		// Calculate the up-level dir count e.g.. (..\..\..\ == 3)
		$up_count	= preg_match_all("/\.\.\\/", $dir_long, $useless);
		$up_count	= pack("v", $up_count);
	
		// Store the short dos dir name (null terminated)
		$dir_short   = preg_replace('/\.\.\\/', '', $dir_long) . "\0";
	
		// Store the long dir name as a wchar string (non-null terminated)
		$dir_long	   = join("\0", split('', $dir_long));
		$dir_long	   = $dir_long . "\0";
	
		// Pack the lengths of the dir strings
		$dir_short_len = pack("V", strlen($dir_short)	  );
		$dir_long_len  = pack("V", strlen($dir_long)	   );
		$stream_len	= pack("V", strlen($dir_long) + 0x06);
	
		// Pack the undocumented parts of the hyperlink stream
		$unknown1 = pack("H*",'D0C9EA79F9BACE118C8200AA004BA90B02000000'	   );
		$unknown2 = pack("H*",'0303000000000000C000000000000046'			   );
		$unknown3 = pack("H*",'FFFFADDE000000000000000000000000000000000000000');
		$unknown4 = pack("v",  0x03											);
	
		// Pack the main data stream
		$data		= pack("vvvv", $row1, $row2, $col1, $col2) .
						  $unknown1	 .
						  $link_type	.
						  $unknown2	 .
						  $up_count	 .
						  $dir_short_len.
						  $dir_short	.
						  $unknown3	 .
						  $stream_len   .
						  $dir_long_len .
						  $unknown4	 .
						  $dir_long	 .
						  $sheet_len	.
						  $sheet		;
	
		// Pack the header data
		$length   = strlen($data);
		$header   = pack("vv", $record, $length);
	
		// Write the packed data
		$this->_append($header. $data);
		return($str_error);
	}
	
	
	/*
	###############################################################################
	#
	# write_url_xxx($row1, $col1, $row2, $col2, $url, $string, $format)
	#
	# Write links to external MS/Novell network drives and shares such as
	# '//NETWORK/share/foo.xls' and '//NETWORK/share/foo.xls#Sheet1!A1'.
	#
	# See also write_url() above for a general description and return values.
	#
	sub _write_url_external_net {
	
		my $this	= shift;
	
		my $record	  = 0x01B8;					   # Record identifier
		my $length	  = 0x00000;					  # Bytes to follow
	
		my $row1		= $_[0];						# Start row
		my $col1		= $_[1];						# Start column
		my $row2		= $_[2];						# End row
		my $col2		= $_[3];						# End column
		my $url		 = $_[4];						# URL string
		my $str		 = $_[5];						# Alternative label
		my $xf		  = $_[6] || $this->{_url_format};# The cell format
	
	
		# Strip URL type and change Unix dir separator to Dos style (if needed)
		#
		$url			=~ s[^external:][];
		$url			=~ s[/][\\]g;
	
	
		# Write the visible label
		($str = $url)   =~ s[\#][ - ] unless defined $str;
		my $str_error   = $this->write_string($row1, $col1, $str, $xf);
		return $str_error if $str_error == -2;
	
	
		# Determine if the link contains a sheet reference and change some of the
		# parameters accordingly.
		# Split the dir name and sheet name (if it exists)
		#
		my ($dir_long , $sheet) = split /\#/, $url;
		my $link_type		   = 0x0103; # Always absolute
		my $sheet_len;
	
		if (defined $sheet) {
			$link_type |= 0x08;
			$sheet_len  = pack("V", length($sheet) + 0x01);
			$sheet	  = join("\0", split('', $sheet));
			$sheet	 .= "\0\0\0";
	}
		else {
			$sheet_len   = '';
			$sheet	   = '';
	}
	
		# Pack the link type
		$link_type	  = pack("V", $link_type);
	
	
		# Make the string null terminated
		$dir_long	   = $dir_long . "\0";
	
	
		# Pack the lengths of the dir string
		my $dir_long_len  = pack("V", length $dir_long);
	
	
		# Store the long dir name as a wchar string (non-null terminated)
		$dir_long	   = join("\0", split('', $dir_long));
		$dir_long	   = $dir_long . "\0";
	
	
		# Pack the undocumented part of the hyperlink stream
		my $unknown1	= pack("H*",'D0C9EA79F9BACE118C8200AA004BA90B02000000');
	
	
		# Pack the main data stream
		my $data		= pack("vvvv", $row1, $row2, $col1, $col2) .
						  $unknown1	 .
						  $link_type	.
						  $dir_long_len .
						  $dir_long	 .
						  $sheet_len	.
						  $sheet		;
	
	
		# Pack the header data
		$length		 = length $data;
		my $header	  = pack("vv",   $record, $length);
	
	
		# Write the packed data
		$this->_append( $header, $data);
	
		return $str_error;
}*/
	
	/**
	* This method is used to set the height and XF format for a row.
	* Writes the  BIFF record ROW.
	*
	* @access public
	* @param integer $row	The row to set
	* @param integer $height Height we are giving to the row. 
	*						Use NULL to set XF without setting height
	* @param mixed   $format XF format we are giving to the row
	*/
	function set_row($row, $height, $format = 0)
	{
		$record	  = 0x0208;			   // Record identifier
		$length	  = 0x0010;			   // Number of bytes to follow
	
		$colMic	  = 0x0000;			   // First defined column
		$colMac	  = 0x0000;			   // Last defined column
		$irwMac	  = 0x0000;			   // Used by Excel to optimise loading
		$reserved	= 0x0000;			   // Reserved
		$grbit	   = 0x01C0;			   // Option flags. (monkey) see $1 do
		$ixfe		= $this->_XF($format); // XF index
	
		// Use set_row($row, NULL, $XF) to set XF without setting height
		if ($height != NULL) {
			$miyRw = $height * 20;  // row height
		}
		else {
			$miyRw = 0xff;		  // default row height is 256
		}
	
		$header   = pack("vv",	   $record, $length);
		$data	 = pack("vvvvvvvv", $row, $colMic, $colMac, $miyRw,
									 $irwMac,$reserved, $grbit, $ixfe);
		$this->_append($header.$data);
	}
	
	/**
	* Writes Excel DIMENSIONS to define the area in which there is data.
	*/
	function _store_dimensions()
	{
		$record	= 0x0000;			   // Record identifier
		$length	= 0x000A;			   // Number of bytes to follow
		$row_min   = $this->dim_rowmin;	// First row
		$row_max   = $this->dim_rowmax;	// Last row plus 1
		$col_min   = $this->dim_colmin;	// First column
		$col_max   = $this->dim_colmax;	// Last column plus 1
		$reserved  = 0x0000;			   // Reserved by Excel
	
		$header	= pack("vv",	$record, $length);
		$data	  = pack("vvvvv", $row_min, $row_max,
								   $col_min, $col_max, $reserved);
		$this->_prepend($header.$data);
	}
	
	/**
	* Write BIFF record Window2.
	*/
	function _store_window2()
	{
		$record		 = 0x023E;	 // Record identifier
		$length		 = 0x000A;	 // Number of bytes to follow
	
		$grbit		  = 0x00B6;	 // Option flags
		$rwTop		  = 0x0000;	 // Top row visible in window
		$colLeft		= 0x0000;	 // Leftmost column visible in window
		$rgbHdr		 = 0x00000000; // Row/column heading and gridline color
	
		// The options flags that comprise $grbit
		$fDspFmla	   = 0;					 // 0 - bit
		$fDspGrid	   = 1;					 // 1
		$fDspRwCol	  = 1;					 // 2
		$fFrozen		= $this->_frozen;		// 3
		$fDspZeros	  = 1;					 // 4
		$fDefaultHdr	= 1;					 // 5
		$fArabic		= 0;					 // 6
		$fDspGuts	   = 1;					 // 7
		$fFrozenNoSplit = 0;					 // 0 - bit
		$fSelected	  = $this->selected;	   // 1
		$fPaged		 = 1;					 // 2
	
		$grbit			 = $fDspFmla;
		$grbit			|= $fDspGrid	   << 1;
		$grbit			|= $fDspRwCol	  << 2;
		$grbit			|= $fFrozen		<< 3;
		$grbit			|= $fDspZeros	  << 4;
		$grbit			|= $fDefaultHdr	<< 5;
		$grbit			|= $fArabic		<< 6;
		$grbit			|= $fDspGuts	   << 7;
		$grbit			|= $fFrozenNoSplit << 8;
		$grbit			|= $fSelected	  << 9;
		$grbit			|= $fPaged		 << 10;
	
		$header  = pack("vv",   $record, $length);
		$data	= pack("vvvV", $grbit, $rwTop, $colLeft, $rgbHdr);
		$this->_append($header.$data);
	}
	
	/**
	* Write BIFF record DEFCOLWIDTH if COLINFO records are in use.
	*/
	function _store_defcol()
	{
		$record   = 0x0055;	  // Record identifier
		$length   = 0x0002;	  // Number of bytes to follow
		$colwidth = 0x0008;	  // Default column width
	
		$header   = pack("vv", $record, $length);
		$data	 = pack("v",  $colwidth);
		$this->_prepend($header.$data);
	}
	
	/**
	* Write BIFF record COLINFO to define column widths
	*
	* Note: The SDK says the record length is 0x0B but Excel writes a 0x0C
	* length record.
	*
	* @param array $col_array This is the only parameter received and is composed of the following:
	*				0 => First formatted column,
	*				1 => Last formatted column,
	*				2 => Col width (8.43 is Excel default),
	*				3 => The optional XF format of the column,
	*				4 => Option flags.
	*/
	function _store_colinfo($col_array)
	{
		if(isset($col_array[0])) {
			$colFirst = $col_array[0];
		}
		if(isset($col_array[1])) {
			$colLast = $col_array[1];
		}
		if(isset($col_array[2])) {
			$coldx = $col_array[2];
		}
		else {
			$coldx = 8.43;
		}
		if(isset($col_array[3])) {
			$format = $col_array[3];
		}
		else {
			$format = 0;
		}
		if(isset($col_array[4])) {
			$grbit = $col_array[4];
		}
		else {
			$grbit = 0;
		}
		$record   = 0x007D;		  // Record identifier
		$length   = 0x000B;		  // Number of bytes to follow
	
		$coldx   += 0.72;			// Fudge. Excel subtracts 0.72 !?
		$coldx   *= 256;			 // Convert to units of 1/256 of a char
	
		$ixfe	 = $this->_XF($format);
		$reserved = 0x00;			// Reserved
	
		$header   = pack("vv",	 $record, $length);
		$data	 = pack("vvvvvC", $colFirst, $colLast, $coldx,
								   $ixfe, $grbit, $reserved);
		$this->_prepend($header.$data);
	}
	
	/**
	* Write BIFF record SELECTION.
	*
	* @param array $array array containing ($rwFirst,$colFirst,$rwLast,$colLast)
	* @see set_selection()
	*/
	function _store_selection($array)
	{
		list($rwFirst,$colFirst,$rwLast,$colLast) = $array;
		$record   = 0x001D;				  // Record identifier
		$length   = 0x000F;				  // Number of bytes to follow
	
		$pnn	  = $this->_active_pane;	 // Pane position
		$rwAct	= $rwFirst;				// Active row
		$colAct   = $colFirst;			   // Active column
		$irefAct  = 0;					   // Active cell ref
		$cref	 = 1;					   // Number of refs
	
		if (!isset($rwLast)) {
			$rwLast   = $rwFirst;	   // Last  row in reference
		}
		if (!isset($colLast)) {
			$colLast  = $colFirst;	  // Last  col in reference
		}
	
		// Swap last row/col for first row/col as necessary
		if ($rwFirst > $rwLast)
		{
			list($rwFirst, $rwLast) = array($rwLast, $rwFirst);
		}
	
		if ($colFirst > $colLast)
		{
			list($colFirst, $colLast) = array($colLast, $colFirst);
		}
	
		$header   = pack("vv",		 $record, $length);
		$data	 = pack("CvvvvvvCC",  $pnn, $rwAct, $colAct,
									   $irefAct, $cref,
									   $rwFirst, $rwLast,
									   $colFirst, $colLast);
		$this->_append($header.$data);
	}
	
	
	/**
	* Write BIFF record EXTERNCOUNT to indicate the number of external sheet
	* references in a worksheet.
	*
	* Excel only stores references to external sheets that are used in formulas.
	* For simplicity we store references to all the sheets in the workbook
	* regardless of whether they are used or not. This reduces the overall
	* complexity and eliminates the need for a two way dialogue between the formula
	* parser the worksheet objects.
	*
	* @param integer $count The number of external sheet references in this worksheet
	*/
	function _store_externcount($count)
	{
		$record   = 0x0016;		  // Record identifier
		$length   = 0x0002;		  // Number of bytes to follow
	
		$header   = pack("vv", $record, $length);
		$data	 = pack("v",  $count);
		$this->_prepend($header.$data);
	}
	
	/**
	* Writes the Excel BIFF EXTERNSHEET record. These references are used by
	* formulas. A formula references a sheet name via an index. Since we store a
	* reference to all of the external worksheets the EXTERNSHEET index is the same
	* as the worksheet index.
	*
	* @param string $sheetname The name of a external worksheet
	*/
	function _store_externsheet($sheetname)
	{
		$record	= 0x0017;		 // Record identifier
	
		// References to the current sheet are encoded differently to references to
		// external sheets.
		//
		if ($this->name == $sheetname) {
			$sheetname = '';
			$length	= 0x02;  // The following 2 bytes
			$cch	   = 1;	 // The following byte
			$rgch	  = 0x02;  // Self reference
		}
		else {
			$length	= 0x02 + strlen($sheetname);
			$cch	   = strlen($sheetname);
			$rgch	  = 0x03;  // Reference to a sheet in the current workbook
		}
	
		$header	 = pack("vv",  $record, $length);
		$data	   = pack("CC", $cch, $rgch);
		$this->_prepend($header.$data.$sheetname);
	}
	
	/**
	* Writes the Excel BIFF PANE record.
	* The panes can either be frozen or thawed (unfrozen).
	* Frozen panes are specified in terms of an integer number of rows and columns.
	* Thawed panes are specified in terms of Excel's units for rows and columns.
	*
	* @param array $panes This is the only parameter received and is composed of the following:
	*					 0 => Vertical split position,
	*					 1 => Horizontal split position
	*					 2 => Top row visible
	*					 3 => Leftmost column visible
	*					 4 => Active pane
	*/
	function _store_panes($panes)
	{
		$y	   = $panes[0];
		$x	   = $panes[1];
		$rwTop   = $panes[2];
		$colLeft = $panes[3];
		if(count($panes) > 4) { // if Active pane was received
			$pnnAct = $panes[4];
		}
		else {
			$pnnAct = NULL;
		}
		$record  = 0x0041;	   // Record identifier
		$length  = 0x000A;	   // Number of bytes to follow
	
		// Code specific to frozen or thawed panes.
		if ($this->_frozen) {
			// Set default values for $rwTop and $colLeft
			if(!isset($rwTop)) {
				$rwTop   = $y;
			}
			if(!isset($colLeft)) {
				$colLeft = $x;
			}
		}
		else {
			// Set default values for $rwTop and $colLeft
			if(!isset($rwTop)) {
				$rwTop   = 0;
			}
			if(!isset($colLeft)) {
				$colLeft = 0;
			}
	
			// Convert Excel's row and column units to the internal units.
			// The default row height is 12.75
			// The default column width is 8.43
			// The following slope and intersection values were interpolated.
			//
			$y = 20*$y	  + 255;
			$x = 113.879*$x + 390;
		}
	
	
		// Determine which pane should be active. There is also the undocumented
		// option to override this should it be necessary: may be removed later.
		//
		if (!isset($pnnAct))
		{
			if ($x != 0 and $y != 0)
				$pnnAct = 0; // Bottom right
			if ($x != 0 and $y == 0)
				$pnnAct = 1; // Top right
			if ($x == 0 and $y != 0)
				$pnnAct = 2; // Bottom left
			if ($x == 0 and $y == 0)
				$pnnAct = 3; // Top left
		}
	
		$this->_active_pane = $pnnAct; // Used in _store_selection
	
		$header	 = pack("vv",	$record, $length);
		$data	   = pack("vvvvv", $x, $y, $rwTop, $colLeft, $pnnAct);
		$this->_append($header.$data);
	}
	
	/**
	* Store the page setup SETUP BIFF record.
	*/
	function _store_setup()
	{
		$record	   = 0x00A1;				  // Record identifier
		$length	   = 0x0022;				  // Number of bytes to follow
	
		$iPaperSize   = $this->_paper_size;	// Paper size
		$iScale	   = $this->_print_scale;   // Print scaling factor
		$iPageStart   = 0x01;				 // Starting page number
		$iFitWidth	= $this->_fit_width;	// Fit to number of pages wide
		$iFitHeight   = $this->_fit_height;   // Fit to number of pages high
		$grbit		= 0x00;				 // Option flags
		$iRes		 = 0x0258;			   // Print resolution
		$iVRes		= 0x0258;			   // Vertical print resolution
		$numHdr	   = $this->_margin_head;  // Header Margin
		$numFtr	   = $this->_margin_foot;   // Footer Margin
		$iCopies	  = 0x01;				 // Number of copies
	
		$fLeftToRight = 0x0;					 // Print over then down
		$fLandscape   = $this->_orientation;	 // Page orientation
		$fNoPls	   = 0x0;					 // Setup not read from printer
		$fNoColor	 = 0x0;					 // Print black and white
		$fDraft	   = 0x0;					 // Print draft quality
		$fNotes	   = 0x0;					 // Print notes
		$fNoOrient	= 0x0;					 // Orientation not set
		$fUsePage	 = 0x0;					 // Use custom starting page
	
		$grbit		   = $fLeftToRight;
		$grbit		  |= $fLandscape	<< 1;
		$grbit		  |= $fNoPls		<< 2;
		$grbit		  |= $fNoColor	  << 3;
		$grbit		  |= $fDraft		<< 4;
		$grbit		  |= $fNotes		<< 5;
		$grbit		  |= $fNoOrient	 << 6;
		$grbit		  |= $fUsePage	  << 7;
	
		$numHdr = pack("d", $numHdr);
		$numFtr = pack("d", $numFtr);
		if ($this->_byte_order) // if it's Big Endian
		{
			$numHdr = strrev($numHdr);
			$numFtr = strrev($numFtr);
		}
	
		$header = pack("vv", $record, $length);
		$data1  = pack("vvvvvvvv", $iPaperSize,
								   $iScale,
								   $iPageStart,
								   $iFitWidth,
								   $iFitHeight,
								   $grbit,
								   $iRes,
								   $iVRes);
		$data2  = $numHdr .$numFtr;
		$data3  = pack("v", $iCopies);
		$this->_prepend($header.$data1.$data2.$data3);
	}
	
	/**
	* Store the header caption BIFF record.
	*/
	function store_header()
	{
		$record  = 0x0014;			   // Record identifier
	
		$str	 = $this->_header;		// header string
		$cch	 = strlen($str);		 // Length of header string
		$length  = 1 + $cch;			 // Bytes to follow
	
		$header	= pack("vv",  $record, $length);
		$data	  = pack("C",   $cch);
	
		$this->_append($header.$data.$str);
	}
	
	/**
	* Store the footer caption BIFF record.
	*/
	function store_footer()
	{
		$record  = 0x0015;			   // Record identifier
	
		$str	 = $this->_footer;	   // Footer string
		$cch	 = strlen($str);		 // Length of footer string
		$length  = 1 + $cch;			 // Bytes to follow
	
		$header	= pack("vv",  $record, $length);
		$data	  = pack("C",   $cch);
	
		$this->_append($header.$data.$str);
	}
	
	/**
	* Store the horizontal centering HCENTER BIFF record.
	*/
	function store_hcenter()
	{
		$record   = 0x0083;			  // Record identifier
		$length   = 0x0002;			  // Bytes to follow
	
		$fHCenter = $this->_hcenter;	  // Horizontal centering
	
		$header	= pack("vv",  $record, $length);
		$data	  = pack("v",   $fHCenter);
	
		$this->_append($header.$data);
	}
	
	/**
	* Store the vertical centering VCENTER BIFF record.
	*/
	function store_vcenter()
	{
		$record   = 0x0084;			  // Record identifier
		$length   = 0x0002;			  // Bytes to follow
	
		$fVCenter = $this->_vcenter;	  // Horizontal centering
	
		$header	= pack("vv", $record, $length);
		$data	  = pack("v", $fVCenter);
		$this->_append($header.$data);
	}
	
	/**
	* Store the LEFTMARGIN BIFF record.
	*/
	function _store_margin_left()
	{
		$record  = 0x0026;				   // Record identifier
		$length  = 0x0008;				   // Bytes to follow
	
		$margin  = $this->_margin_left;	   // Margin in inches
	
		$header	= pack("vv",  $record, $length);
		$data	  = pack("d",   $margin);
		if ($this->_byte_order) // if it's Big Endian
		{ 
			$data = strrev($data);
		}
	
		$this->_append($header.$data);
	}
	
	/**
	* Store the RIGHTMARGIN BIFF record.
	*/
	function _store_margin_right()
	{
		$record  = 0x0027;				   // Record identifier
		$length  = 0x0008;				   // Bytes to follow
	
		$margin  = $this->_margin_right;	  // Margin in inches
	
		$header	= pack("vv",  $record, $length);
		$data	  = pack("d",   $margin);
		if ($this->_byte_order) // if it's Big Endian
		{ 
			$data = strrev($data);
		}
	
		$this->_append($header.$data);
	}
	
	/**
	* Store the TOPMARGIN BIFF record.
	*/
	function _store_margin_top()
	{
		$record  = 0x0028;				   // Record identifier
		$length  = 0x0008;				   // Bytes to follow
	
		$margin  = $this->_margin_top;		// Margin in inches
	
		$header	= pack("vv",  $record, $length);
		$data	  = pack("d",   $margin);
		if ($this->_byte_order) // if it's Big Endian
		{ 
			$data = strrev($data);
		}
	
		$this->_append($header.$data);
	}
	
	/**
	* Store the BOTTOMMARGIN BIFF record.
	*/
	function _store_margin_bottom()
	{
		$record  = 0x0029;				   // Record identifier
		$length  = 0x0008;				   // Bytes to follow
	
		$margin  = $this->_margin_bottom;	 // Margin in inches
	
		$header	= pack("vv",  $record, $length);
		$data	  = pack("d",   $margin);
		if ($this->_byte_order) // if it's Big Endian
		{ 
			$data = strrev($data);
		}
	
		$this->_append($header.$data);
	}

	/**
	* This is an Excel97/2000 method. It is required to perform more complicated
	* merging than the normal set_align('merge'). It merges the area given by 
	* its arguments.
	*
	* @access public
	* @param integer $first_row First row of the area to merge
	* @param integer $first_col First column of the area to merge
	* @param integer $last_row  Last row of the area to merge
	* @param integer $last_col  Last column of the area to merge
	*/
	function merge_cells($first_row, $first_col, $last_row, $last_col)
	{
		$record  = 0x00E5;				   // Record identifier
		$length  = 0x000A;				   // Bytes to follow
		$cref	 = 1;					   // Number of refs

		// Swap last row/col for first row/col as necessary
		if ($first_row > $last_row) {
			list($first_row, $last_row) = array($last_row, $first_row);
		}
	
		if ($first_col > $last_col) {
			list($first_col, $last_col) = array($last_col, $first_col);
		}
	
		$header   = pack("vv",	$record, $length);
		$data	 = pack("vvvvv", $cref, $first_row, $last_row,
								  $first_col, $last_col);
	
		$this->_append($header.$data);
	}
	
	/**
	* Write the PRINTHEADERS BIFF record.
	*/
	function _store_print_headers()
	{
		$record	  = 0x002a;				   // Record identifier
		$length	  = 0x0002;				   // Bytes to follow
	
		$fPrintRwCol = $this->_print_headers;	 // Boolean flag
	
		$header	  = pack("vv", $record, $length);
		$data		= pack("v", $fPrintRwCol);
		$this->_prepend($header.$data);
	}
	
	/**
	* Write the PRINTGRIDLINES BIFF record. Must be used in conjunction with the
	* GRIDSET record.
	*/
	function _store_print_gridlines()
	{
		$record	  = 0x002b;					// Record identifier
		$length	  = 0x0002;					// Bytes to follow
	
		$fPrintGrid  = $this->_print_gridlines;	// Boolean flag
	
		$header	  = pack("vv", $record, $length);
		$data		= pack("v", $fPrintGrid);
		$this->_prepend($header.$data);
	}
	
	/**
	* Write the GRIDSET BIFF record. Must be used in conjunction with the
	* PRINTGRIDLINES record.
	*/
	function _store_gridset()
	{
		$record	  = 0x0082;						// Record identifier
		$length	  = 0x0002;						// Bytes to follow
	
		$fGridSet	= !($this->_print_gridlines);	 // Boolean flag
	
		$header	  = pack("vv",  $record, $length);
		$data		= pack("v",   $fGridSet);
		$this->_prepend($header.$data);
	}
	
	/**
	* Write the WSBOOL BIFF record, mainly for fit-to-page. Used in conjunction
	* with the SETUP record.
	*/
	function _store_wsbool()
	{
		$record	  = 0x0081;   // Record identifier
		$length	  = 0x0002;   // Bytes to follow
	
		// The only option that is of interest is the flag for fit to page. So we
		// set all the options in one go.
		//
		if ($this->_fit_page) {
			$grbit = 0x05c1;
		}
		else {
			$grbit = 0x04c1;
		}
	
		$header	  = pack("vv", $record, $length);
		$data		= pack("v",  $grbit);
		$this->_prepend($header.$data);
	}
	
	
	/**
	* Write the HORIZONTALPAGEBREAKS BIFF record.
	*/
	function _store_hbreak()
	{
		// Return if the user hasn't specified pagebreaks
		if(empty($this->_hbreaks)) {
			return;
		}
	
		// Sort and filter array of page breaks
		$breaks = $this->_hbreaks;
		sort($breaks,SORT_NUMERIC);
		if($breaks[0] == 0) { // don't use first break if it's 0
			array_shift($breaks);
		}
	
		$record  = 0x001b;			   // Record identifier
		$cbrk	= count($breaks);	   // Number of page breaks
		$length  = ($cbrk + 1) * 2;	  // Bytes to follow
	
		$header  = pack("vv", $record, $length);
		$data	= pack("v",  $cbrk);
	
		// Append each page break
		foreach($breaks as $break) {
			$data .= pack("v", $break);
		}
	
		$this->_prepend($header.$data);
	}
	
	
	/**
	* Write the VERTICALPAGEBREAKS BIFF record.
	*/
	function _store_vbreak()
	{
		// Return if the user hasn't specified pagebreaks
		if(empty($this->_vbreaks)) {
			return;
		}
	
		// 1000 vertical pagebreaks appears to be an internal Excel 5 limit.
		// It is slightly higher in Excel 97/200, approx. 1026
		$breaks = array_slice($this->_vbreaks,0,1000);
	
		// Sort and filter array of page breaks
		sort($breaks,SORT_NUMERIC);
		if($breaks[0] == 0) { // don't use first break if it's 0
			array_shift($breaks);
		}
	
		$record  = 0x001a;			   // Record identifier
		$cbrk	= count($breaks);	   // Number of page breaks
		$length  = ($cbrk + 1) * 2;	  // Bytes to follow
	
		$header  = pack("vv",  $record, $length);
		$data	= pack("v",   $cbrk);
	
		// Append each page break
		foreach ($breaks as $break) {
			$data .= pack("v", $break);
		}
	
		$this->_prepend($header.$data);
	}
	
	/**
	* Set the Biff PROTECT record to indicate that the worksheet is protected.
	*/
	function _store_protect()
	{
		// Exit unless sheet protection has been specified
		if($this->_protect == 0) {
			return;
		}
	
		$record	  = 0x0012;			 // Record identifier
		$length	  = 0x0002;			 // Bytes to follow
	
		$fLock	   = $this->_protect;	// Worksheet is protected
	
		$header	  = pack("vv", $record, $length);
		$data		= pack("v",  $fLock);
	
		$this->_prepend($header.$data);
	}
	
	/**
	* Write the worksheet PASSWORD record.
	*/
	function _store_password()
	{
		// Exit unless sheet protection and password have been specified
		if(($this->_protect == 0) or (!isset($this->_password))) {
			return;
		}
	
		$record	  = 0x0013;			   // Record identifier
		$length	  = 0x0002;			   // Bytes to follow
	
		$wPassword   = $this->_password;	 // Encoded password
	
		$header	  = pack("vv", $record, $length);
		$data		= pack("v",  $wPassword);
	
		$this->_prepend($header.$data);
	}
	
	/**
	* Insert a 24bit bitmap image in a worksheet. The main record required is
	* IMDATA but it must be proceeded by a OBJ record to define its position.
	*
	* @access public
	* @param integer $row	 The row we are going to insert the bitmap into
	* @param integer $col	 The column we are going to insert the bitmap into
	* @param string  $bitmap  The bitmap filename
	* @param integer $x	   The horizontal position (offset) of the image inside the cell.
	* @param integer $y	   The vertical position (offset) of the image inside the cell.
	* @param integer $scale_x The horizontal scale
	* @param integer $scale_y The vertical scale
	*/
	function insert_bitmap($row, $col, $bitmap, $x = 0, $y = 0, $scale_x = 1, $scale_y = 1)
	{
		list($width, $height, $size, $data) = $this->_process_bitmap($bitmap);
	
		// Scale the frame of the image.
		$width  *= $scale_x;
		$height *= $scale_y;
	
		// Calculate the vertices of the image and write the OBJ record
		$this->_position_image($col, $row, $x, $y, $width, $height);
	
		// Write the IMDATA record to store the bitmap data
		$record	  = 0x007f;
		$length	  = 8 + $size;
		$cf		  = 0x09;
		$env		 = 0x01;
		$lcb		 = $size;
	
		$header	  = pack("vvvvV", $record, $length, $cf, $env, $lcb);
		$this->_append($header.$data);
	}
	
	/**
	* Calculate the vertices that define the position of the image as required by
	* the OBJ record.
	*
	*		 +------------+------------+
	*		 |	 A	  |	  B	 |
	*   +-----+------------+------------+
	*   |	 |(x1,y1)	 |			|
	*   |  1  |(A1)._______|______	  |
	*   |	 |	|			  |	 |
	*   |	 |	|			  |	 |
	*   +-----+----|	BITMAP	|-----+
	*   |	 |	|			  |	 |
	*   |  2  |	|______________.	 |
	*   |	 |			|		(B2)|
	*   |	 |			|	 (x2,y2)|
	*   +---- +------------+------------+
	*
	* Example of a bitmap that covers some of the area from cell A1 to cell B2.
	*
	* Based on the width and height of the bitmap we need to calculate 8 vars:
	*	 $col_start, $row_start, $col_end, $row_end, $x1, $y1, $x2, $y2.
	* The width and height of the cells are also variable and have to be taken into
	* account.
	* The values of $col_start and $row_start are passed in from the calling
	* function. The values of $col_end and $row_end are calculated by subtracting
	* the width and height of the bitmap from the width and height of the
	* underlying cells.
	* The vertices are expressed as a percentage of the underlying cell width as
	* follows (rhs values are in pixels):
	*
	*	   x1 = X / W *1024
	*	   y1 = Y / H *256
	*	   x2 = (X-1) / W *1024
	*	   y2 = (Y-1) / H *256
	*
	*	   Where:  X is distance from the left side of the underlying cell
	*			   Y is distance from the top of the underlying cell
	*			   W is the width of the cell
	*			   H is the height of the cell
	*
	* @note  the SDK incorrectly states that the height should be expressed as a
	*		percentage of 1024.
	* @param integer $col_start Col containing upper left corner of object
	* @param integer $row_start Row containing top left corner of object
	* @param integer $x1		Distance to left side of object
	* @param integer $y1		Distance to top of object
	* @param integer $width	 Width of image frame
	* @param integer $height	Height of image frame
	*/
	function _position_image($col_start, $row_start, $x1, $y1, $width, $height)
	{
		// Initialise end cell to the same as the start cell
		$col_end	= $col_start;  // Col containing lower right corner of object
		$row_end	= $row_start;  // Row containing bottom right corner of object
	
		// Zero the specified offset if greater than the cell dimensions
		if ($x1 >= $this->size_col($col_start))
		{
			$x1 = 0;
		}
		if ($y1 >= $this->size_row($row_start))
		{
			$y1 = 0;
		}
	
		$width	  = $width  + $x1 -1;
		$height	 = $height + $y1 -1;
	
		// Subtract the underlying cell widths to find the end cell of the image
		while ($width >= $this->size_col($col_end)) {
			$width -= $this->size_col($col_end);
			$col_end++;
		}
	
		// Subtract the underlying cell heights to find the end cell of the image
		while ($height >= $this->size_row($row_end)) {
			$height -= $this->size_row($row_end);
			$row_end++;
		}
	
		// Bitmap isn't allowed to start or finish in a hidden cell, i.e. a cell
		// with zero eight or width.
		//
		if ($this->size_col($col_start) == 0)
			return;
		if ($this->size_col($col_end)   == 0)
			return;
		if ($this->size_row($row_start) == 0)
			return;
		if ($this->size_row($row_end)   == 0)
			return;
	
		// Convert the pixel values to the percentage value expected by Excel
		$x1 = $x1	 / $this->size_col($col_start)   * 1024;
		$y1 = $y1	 / $this->size_row($row_start)   *  256;
		$x2 = $width  / $this->size_col($col_end)	 * 1024; // Distance to right side of object
		$y2 = $height / $this->size_row($row_end)	 *  256; // Distance to bottom of object
	
		$this->_store_obj_picture( $col_start, $x1,
								  $row_start, $y1,
								  $col_end, $x2,
								  $row_end, $y2
								);
	}
	
	/**
	* Convert the width of a cell from user's units to pixels. By interpolation
	* the relationship is: y = 7x +5. If the width hasn't been set by the user we
	* use the default value. If the col is hidden we use a value of zero.
	*
	* @param integer  $col The column 
	* @return integer The width in pixels
	*/
	function size_col($col)
	{
		// Look up the cell value to see if it has been changed
		if (isset($this->col_sizes[$col])) {
			if ($this->col_sizes[$col] == 0) {
				return(0);
			}
			else {
				return(floor(7 * $this->col_sizes[$col] + 5));
			}
		}
		else {
			return(64);
		}
	}
	
	/**
	* Convert the height of a cell from user's units to pixels. By interpolation
	* the relationship is: y = 4/3x. If the height hasn't been set by the user we
	* use the default value. If the row is hidden we use a value of zero. (Not
	* possible to hide row yet).
	*
	* @param integer $row The row
	* @return integer The width in pixels
	*/
	function size_row($row)
	{
		// Look up the cell value to see if it has been changed
		if (isset($this->row_sizes[$row])) {
			if ($this->row_sizes[$row] == 0) {
				return(0);
			}
			else {
				return(floor(4/3 * $this->row_sizes[$row]));
			}
		}
		else {
			return(17);
		}
	}
	
	/**
	* Store the OBJ record that precedes an IMDATA record. This could be generalise
	* to support other Excel objects.
	*
	* @param integer $colL Column containing upper left corner of object
	* @param integer $dxL  Distance from left side of cell
	* @param integer $rwT  Row containing top left corner of object
	* @param integer $dyT  Distance from top of cell
	* @param integer $colR Column containing lower right corner of object
	* @param integer $dxR  Distance from right of cell
	* @param integer $rwB  Row containing bottom right corner of object
	* @param integer $dyB  Distance from bottom of cell
	*/
	function _store_obj_picture($colL,$dxL,$rwT,$dyT,$colR,$dxR,$rwB,$dyB)
	{
		$record	  = 0x005d;   // Record identifier
		$length	  = 0x003c;   // Bytes to follow
	
		$cObj		= 0x0001;   // Count of objects in file (set to 1)
		$OT		  = 0x0008;   // Object type. 8 = Picture
		$id		  = 0x0001;   // Object ID
		$grbit	   = 0x0614;   // Option flags
	
		$cbMacro	 = 0x0000;   // Length of FMLA structure
		$Reserved1   = 0x0000;   // Reserved
		$Reserved2   = 0x0000;   // Reserved
	
		$icvBack	 = 0x09;	 // Background colour
		$icvFore	 = 0x09;	 // Foreground colour
		$fls		 = 0x00;	 // Fill pattern
		$fAuto	   = 0x00;	 // Automatic fill
		$icv		 = 0x08;	 // Line colour
		$lns		 = 0xff;	 // Line style
		$lnw		 = 0x01;	 // Line weight
		$fAutoB	  = 0x00;	 // Automatic border
		$frs		 = 0x0000;   // Frame style
		$cf		  = 0x0009;   // Image format, 9 = bitmap
		$Reserved3   = 0x0000;   // Reserved
		$cbPictFmla  = 0x0000;   // Length of FMLA structure
		$Reserved4   = 0x0000;   // Reserved
		$grbit2	  = 0x0001;   // Option flags
		$Reserved5   = 0x0000;   // Reserved
	
	
		$header	  = pack("vv", $record, $length);
		$data		= pack("V", $cObj);
		$data	   .= pack("v", $OT);
		$data	   .= pack("v", $id);
		$data	   .= pack("v", $grbit);
		$data	   .= pack("v", $colL);
		$data	   .= pack("v", $dxL);
		$data	   .= pack("v", $rwT);
		$data	   .= pack("v", $dyT);
		$data	   .= pack("v", $colR);
		$data	   .= pack("v", $dxR);
		$data	   .= pack("v", $rwB);
		$data	   .= pack("v", $dyB);
		$data	   .= pack("v", $cbMacro);
		$data	   .= pack("V", $Reserved1);
		$data	   .= pack("v", $Reserved2);
		$data	   .= pack("C", $icvBack);
		$data	   .= pack("C", $icvFore);
		$data	   .= pack("C", $fls);
		$data	   .= pack("C", $fAuto);
		$data	   .= pack("C", $icv);
		$data	   .= pack("C", $lns);
		$data	   .= pack("C", $lnw);
		$data	   .= pack("C", $fAutoB);
		$data	   .= pack("v", $frs);
		$data	   .= pack("V", $cf);
		$data	   .= pack("v", $Reserved3);
		$data	   .= pack("v", $cbPictFmla);
		$data	   .= pack("v", $Reserved4);
		$data	   .= pack("v", $grbit2);
		$data	   .= pack("V", $Reserved5);
	
		$this->_append($header.$data);
	}
	
	/**
	* Convert a 24 bit bitmap into the modified internal format used by Windows.
	* This is described in BITMAPCOREHEADER and BITMAPCOREINFO structures in the
	* MSDN library.
	*
	* @param string $bitmap The bitmap to process
	* @return array Array with data and properties of the bitmap
	*/
	function _process_bitmap($bitmap)
	{
		// Open file.
		$bmp_fd = fopen($bitmap,"rb");
		if (!$bmp_fd) {
			die("Couldn't import $bitmap");
		}
			
		// Slurp the file into a string.
		$data = fread($bmp_fd, filesize($bitmap));
	
		// Check that the file is big enough to be a bitmap.
		if (strlen($data) <= 0x36) {
			die("$bitmap doesn't contain enough data.\n");
		}
	
		// The first 2 bytes are used to identify the bitmap.
		$identity = unpack("A2", $data);
		if ($identity[''] != "BM") {
			die("$bitmap doesn't appear to be a valid bitmap image.\n");
		}
	
		// Remove bitmap data: ID.
		$data = substr($data, 2);
	
		// Read and remove the bitmap size. This is more reliable than reading
		// the data size at offset 0x22.
		//
		$size_array   = unpack("V", substr($data, 0, 4));
		$size   = $size_array[''];
		$data   = substr($data, 4);
		$size  -= 0x36; // Subtract size of bitmap header.
		$size  += 0x0C; // Add size of BIFF header.
	
		// Remove bitmap data: reserved, offset, header length.
		$data = substr($data, 12);
	
		// Read and remove the bitmap width and height. Verify the sizes.
		$width_and_height = unpack("V2", substr($data, 0, 8));
		$width  = $width_and_height[1];
		$height = $width_and_height[2];
		$data   = substr($data, 8);
		if ($width > 0xFFFF) { 
			die("$bitmap: largest image width supported is 65k.\n");
		}
		if ($height > 0xFFFF) { 
			die("$bitmap: largest image height supported is 65k.\n");
		}
	
		// Read and remove the bitmap planes and bpp data. Verify them.
		$planes_and_bitcount = unpack("v2", substr($data, 0, 4));
		$data = substr($data, 4);
		if ($planes_and_bitcount[2] != 24) { // Bitcount
			die("$bitmap isn't a 24bit true color bitmap.\n");
		}
		if ($planes_and_bitcount[1] != 1) {
			die("$bitmap: only 1 plane supported in bitmap image.\n");
		}
	
		// Read and remove the bitmap compression. Verify compression.
		$compression = unpack("V", substr($data, 0, 4));
		$data = substr($data, 4);
	  
		//$compression = 0;
		if ($compression[""] != 0) {
			die("$bitmap: compression not supported in bitmap image.\n");
		}
	
		// Remove bitmap data: data size, hres, vres, colours, imp. colours.
		$data = substr($data, 20);
	
		// Add the BITMAPCOREHEADER data
		$header  = pack("Vvvvv", 0x000c, $width, $height, 0x01, 0x18);
		$data	= $header . $data;
	
		return (array($width, $height, $size, $data));
	}
	
	/**
	* Store the window zoom factor. This should be a reduced fraction but for
	* simplicity we will store all fractions with a numerator of 100.
	*/
	function _store_zoom()
	{
		// If scale is 100 we don't need to write a record
		if ($this->_zoom == 100) {
			return;
		}
	
		$record	  = 0x00A0;			   // Record identifier
		$length	  = 0x0004;			   // Bytes to follow
	
		$header	  = pack("vv", $record, $length);
		$data		= pack("vv", $this->_zoom, 100);
		$this->_append($header.$data);
	}
}
?>